Sono-bromination of aromatic compounds based on the ultrasonic advanced oxidation processes

Abstract

A novel, mild "sono-halogenation" of various aromatic compounds with potassium halide was investigated under ultrasound in a biphasic carbon tetrachloride/water medium. The feasibility study was first undertaken with the potassium bromide and then extended to chloride and iodide analogues. This methodology could be considered as a new expansion of the ultrasonic advanced oxidation processes (UAOPs) into a synthetic aspect as the developed methodology is linked to the sonolytic disappearance of carbon tetrachloride. Advantages of the present method are not only that the manipulation of the bromination is simple and green, but also that the halogenating agents used are readily available, inexpensive, and easy-handling.

Ultrasound-Assisted Bromination of Aromatic Rings Using NaBr/H2 O2 System

“…Most of these protocols involve long reaction time using conventional activation methods, such as heating with stirring. One example in the literature involves the use of ultrasound in an oxidative halogenation where a molybdate catalyst, with KBr and H 2 O 2 , is required, displaying reactions time as long as 2 to 4 hours. Others metal catalysed aromatic halogenation can be found in the literature …”

“…It indicates an electrophilic mechanism of the reaction rather than a radical pathway. It is believed that ultrasonic waves help the in situ formation of positive halogen species, such as BrOH, Br 2 and/or Br 3 − ,, by the oxidation of NaBr and then the reaction follows a typical aromatic electrophilic substitution.…”

Bromination of Aromatic Amines

“…"Sono-halogenation" of aromatic amines with potassium bromide has been carried out under ultrasound in two-phase carbon tetrachloride/water (CCl4/H2O) conditions [15] and nuclear bromination with an electrochemical method has been carried out by two-phase electrolysis (scheme 10) [16]. An electrolyte bromine source (solution of 5% HBr with 50-60% NaBr) was used as an upper phase.…”

Ultrasound assisted synthesis of hybrid quinoline-imidazole derivatives: a green synthetic approach

“…Compared with conventional thermal heating (TH), the use of US in chemical reactions has some crucial advantages, such as higher yields, better product purity, the possibility to obtain better selectivity and higher reactivity, and reduced reaction times. [1][2][3][4][5][6][7][8][9][10][11][31][32][33]36 In addition, due to milder reaction conditions, less or suppressed side reactions, energy saving nature, and the use of small amounts of solvents, the reactions become eco-friendly. 6,[9][10][11]27,28 Quinoline and imidazole derivatives are structural scaffolds of huge importance from pharmacological, industrial, and synthetic points of view.…”